Horizontal boring machines are used to install utility services or other products underground. Horizontal boring eliminates surface disruption along the length of the project, except at the entry and exit points, and reduces the likelihood of damaging previously buried products. Skilled and experienced crews have greatly increased the efficiency and accuracy of boring operations. However, there is a continuing need for more automated boring machines which reduce the need for operator intervention and thereby increase the efficiency of boring underground.
The boring operation is a process of using a boring machine to advance a drill string through the earth along a desired path. The boring machine generally comprises a frame, a drive system mounted on the frame and connected to one end of the drill string, and a boring tool connected to the other end of the drill string. The drive system provides thrust and rotation needed to advance the drill string and the boring tool through the earth. The drive system generally has a motor to rotate the drill string and separate motor to push the drill string. The drill string is advanced in a straight line by simultaneously rotating and pushing the drill string through the earth. To control the direction of the borehole, a slant-faced drill bit may be used. When the direction of the borehole must be changed, the drill bit is positioned with the slant-face pointed in the desired direction. The drill string is then pushed through the earth without rotation, so that the slant-face causes the drill string to deflect in the desired direction.
The drill string is generally comprised of a plurality of drill pipe sections joined together at threaded connections. As the boring operation proceeds, the drill string is lengthened by repeatedly adding pipe sections to the drill string. Each time a pipe section is added to the drill string the pipe section being added is aligned with the drill string, the threaded joints are lubricated to ensure proper connections, and the connections between the drive system, the pipe section, and the drill string are secured. The process is the same each time a pipe section is added to the drill string.
When the boring operation is completed, the drill string is pulled back through the borehole, generally with the utility line or product to be installed underground connected to the end of the drill string. Many times, the original borehole must be enlarged to accommodate the product being installed. The enlarging of the borehole is accomplished by adding a backreaming tool between the end of the drill string and the product being pulled through the borehole. During this backreaming operation, pipe sections are removed from the drill string as the drill string gets shorter. Each time a pipe section is taken from the drill string, the connections between the drive system, the pipe section, and the drill string are broken, the pipe section is removed from the boring machine, and the threaded joint of the drill string is lubricated before the drive system is reconnected to the drill string so the backreaming operation can continue. As is the case with the addition of pipe sections to the drill string, the process is repetitive. As one skilled in the art will appreciate, efficient and economic machines for adding and removing pipe sections are a present need in the industry.